Computer begins starting then turns off then repeats

My Computer begins starting then turns off then repeats. Yesterday evening I went to my computer and it was off though I remember it being left on. I pressed on and it began starting but died and repeated trying to start. It does not reach post, I cannot access BIOS or F9. Removing memory does not cause no memory beep. Unplugging hard drive (SSD) does not have any effect, it does not get far enough for it to make a difference. I am beginning to think that the power supply may be defective. Opinions and suggestions are appreciated. I also just cleaned out dust though it was not bad and has always run cool.History: The machine has worked exceptionally well since built last summer. The only prior problem has been wake from sleep issue that SSD firmware update made somewhat better.Components:GA-Z97X-UD3H vers.1 - F7 BIOSi5-4690K running at stock speedsGTX750Ti factory OCOCZ Vertex 460 as boot/OS, ProgramsWD 1TB black storageGSkill Sniper DDR3-2133 CL9-11-10-28 Two 2x4 packs (16GB) 1.65V at XMP settingsNoctura air cooler (runs very cool - always)

Jeff: Sorry if I was not clear but the cleaning was a just in case after it began the problem.

Always: I will have to see if machine that is not being used happen to have the newer 24pin/8pin motherboard connectors, if so then I will just try that. If not power supply then it would be motherboard though visual inspection shows it looks good, including all visible capacitors.

The Windows 98 SE computer is an old notebook computer thatwas my only machine for a while a few years ago, and had set upbeside my Windows 7 desktop until 5 months ago. But then I hadto move and there is no room here for the desktop. I acquired anAndroid tablet to fill in, but decided to set up the notebook since ithas some files I wanted.

I was surprised to discover that I can't even access my own webpages with it and IE 5.5 and dialup. My web pages are the simplestplain vanilla HTML possible, and small. Yet the home page stoppedloading after one or two images and a couple of lines of text. I wasable to post here okay, but it was terribly clumsy. Using this Androidtablet is awfully clumsy, too, but not as bad as that mess.

I want to know whether your problem is with the power supply ormotherboard, since my Windows 7 desktop has had an intermittantproblem with video going out at startup that I wasn't able to pin downover five years since I built it. It could be the power supply, the videoboard, or the motherboard. I might have damaged the motherboardwhile trying to push the stock Intel CPU cooler into place. I was neverable to get it to go in, and bought a Thermaltake cooler that screwedin easily.

I have been working and lots of things to do here a well so I have not had the time to even look for a suitable power supply here. I am typing on the older Family desktop, a Core2 era with Windows 7 on it which is not too bad except that I dislike the keyboard in here and there are are possibly 30 browser tabs open that I am not 'allowed' to close. Needless to say it is not what I would prefer but it works. I will update as soon as I get a bit of time, probably Friday.

Update: I tried a new power supply. No difference.I tried systematically unplugging components (HD, SSD, DVD, Graphics card, connectors to front panel, fans, etc.) and tried everything except the CPU itself.Next I cleared the CMOS and the system stayed on!!!I moved it back into room and plugged everything in, reset BIOS settings and rebooted.Keyboard and mouse worked in BIOS set up and prior to Windows loading but would not let me type in password. I rebooted into Safe Mode (worked in safe mode) and reinstalled USB driver from Gigabyte and rebooted. All works good now.

Thank you all for suggestions. I knew that I just had to systematically eliminate all possibilities and thought that if anyone had a similar problem recently I might find a quick solution that I had not thought of and saved the time waiting for a morning off concentrate on it.

Thanks again and I hope that someone will find this helpful with a similar problem.

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